FATTY SUBSTANCES (GENERAL METHODS) 389
solid acetyl compound which, when purified and recrystallised from alcohol,
melts at 114-115°. If a solution of a little cholesterol in 2 c.c. of chloroform
is shaken with an equal volume of concentrated sulphuric acid, the chloro-
form solution assumes a red coloration,
which soon changes to cherry-red and
then to violet-red, this persisting for some
days, whilst the acid liquid turns reddish
brown ; if a few drops of the chloroform
solution are shaken in a porcelain dish, the
colour changes successively to blue, green
and dirty yellow.
Phytosterol or sitosterol (cholesterol from
plants] occurs in fatty substances of vege-
table origin. It dissolves in alcohol, from
which it crystallises in tufts of broad,
blunt-ended needles, having the micro-
scopic appearance of elongated, blunted plates (Fig. 55), m.pt. 135-144°.
When boiled with acetic anhydride, phytosterol also gives an acetyl-com-
pound, m.pt. 125—137° (purified and recrystallised). With chloroform and
sulphuric acid it behaves like cholesterol.
When a mixture of cholesterol and phytosterol—which may be obtained
from a mixture of animal and vegetable fats or oils— is crystallised from
alcohol, the crystals show the predominant form of the phytosterol (Fig.
56) and melt at temperatures intermediate to the melting points of choles-
terol and phytosterol (see also Lard).
2. Paraffin Wax. Ceresine.—These are solid and are insoluble in
alcohol, aniline and acetic anhydride,1 and hence distinguishable from the
3. Mineral Oils, Tar Oils, Resin Oils.—These are liquids and are
readily recognisable by their appearance and odour. Resin oils are also
characterised by their reaction with sulphuric acid (see Resin Oils) or by then-
rotatory power (4- 30° to 4- 50° in a 200 mm. tube), and the mineral oils
* If acetic anhydride is boiled for a long time with paraffin wax or ceresine, the
latter dissolves, but the solution becomes turbid as soon as the flame is removed.le matters which may be extracted from fats in this